"error" - good or bad result
"total_hashrate" - hashrate of all your workers (MHs)
"total_hashrate_calculated" - calculated hashrate based on shares. Maybe different due to nature of mining (MHs)
"wallet" - requested account

and data per worker

"workers": {
"workername": {
"alive" - last share sended not more then 5 minutes ago
"hashrate" - hashrate in MHs
"hashrate_below_threshold" - if true your rigs send under 60% of usually amount of shares.
"hashrate_calculated" - calculation based on shares of last 30 minutes.
For new started workers first 10 minutes no stat.
Zero value for workers without valid shares last 30 minutes.
"last_submit" - time of last submit, GMT+1
"second_since_submit" - seconds since last submit till now
"worker" - repeat of workername
}
}